1. Field of the Invention
The present invention relates to a method of compensation for a cyclical input signal. In a further aspect, the invention relates to an arrangement for compensation of a cyclical input signal. The invention has particular application in engine control to compensate behavior changes of a sensor, such as offset and sensitivity, during operation of said sensor, due to for example ambient temperature changes.
2. Description of the Related Art
Pressure sensors are widely used in combustion systems. Given that pressure sensors are often used in harsh environments, techniques for data correction that take into account conditions of operation are often required.
Pressure sensors exhibit an offset voltage, which is the output voltage of a sensor when no pressure is applied. The output voltage will vary as a function of temperature (that is, has a certain “offset voltage temperature characteristic”). The offset voltage temperature characteristic defines the variation of the offset voltage with changes in ambient temperature of the sensor.
Modern engines could use closed loop combustion for several reasons like CO2 or emission reduction. The pressure inside the cylinder gives information about the timing, cleanliness and effectiveness of the combustion. With knowledge of the cylinder pressure NOx and particulate emissions, heat release and torque can be measured and controlled, it is very easy to determine combustion onset and other such parameters. Well known examples of combustion parameters are heat release points and indicated mean effective pressure (IMEP) values.
One method for compensating output of a pressure sensor for the variability arising during operation is provided in U.S. Pat. No. 7,913,536, entitled “Compensation Arrangement and Method for Operation thereof,” the entire disclosure of which is incorporated herein in its entirety. While the techniques provided offer improvements over the prior art, it would be advantageous to account for drift in the signal from a pressure sensor where the cycles occur in a more rapid fashion.
What are needed are methods and apparatus to improve correction of pressure sensor offset drift.